As this type of rotary cutter, there is conventionally proposed one including a cutting head formed of a disk-shaped base plate having at its center a drive shaft coupling portion and provided at its outer periphery with a sidewall and a substantially cylindrical protecting cover detachably mounted to the sidewall to face the base plate. Inside the cutting head, fastening means for fastening a cord of a predetermined length and for mowing grass, lawn, and the like by rotation is provided to the disk-shaped base plate. The fastening means presses and fixes the cord onto a pressing wall provided to the sidewall of the base plate by an elastic member such as a coil spring and a torsion spring and a fastening member in a shape of a cam, a cylindrical rod, or the like (see U.S. Pat. No. 5,896,666).
There is also a known rotary cutter, as shown in FIGS. 4 and 5, including a disk-shaped cutting head main body 10 formed of a case 10-1 having a drive shaft coupling shaft tube portion 10-1a at its central portion and a cover 10-2 having a through hole 10-2a for the drive shaft coupling shaft tube portion 10-1a at its central portion and paring up with the case 10-1. At an outer peripheral end portion of the cutting head main body 10, fastening means 11 for fastening cords 12 of predetermined length are provided. When the cord 12 of the predetermined length inserted into the cutting head main body 10 is worn out, the cord is removed from the cutting head main body 10 and replaced with a new cord. Each of the cord fastening means 11 of the rotary cutter is disposed in a cord guide 11-1 provided in an opening formed in a sidewall of the cutting head main body 10 and is formed of a pair of ratchets 11-2, each of the ratchets being constantly applied with a rotational force in a certain direction by a spring 11-3 pivoted for turning on and mounted from outside to a support shaft 10-3 protruding from the cover 10-2 of the cutting head main body 10 to fasten the cover 10-2 and the case 10-1 together by using a fastening screw 15. In other words, in the cord fastening means 11, one end of the cord 12 of the predetermined length inserted into the cutting head main body 10 from a cord lead-out outlet (cord guide) 11-1 is clamped and fastened by the pair of ratchets 11-2. Therefore, in the case of this rotary cutter, a space 10-4 for holding the code 12 to remove and replace it is provided between the ratchets 11-2 and the drive shaft coupling shaft tube portion 10-1a at the central portion of the cutting head main body. A drive shaft 13 of the cutting head main body 1 is mounted by a coupling bolt 16 through a lid body 14 covering a bottom portion of the cutting head main body 11 as shown in FIG. 4.